Drill bit and method of manufacturing a drill bit
The drill bit with three main cutting surfaces and edge-free surfaces addresses positioning accuracy and wear issues by eliminating transverse cutting surfaces and edges, enhancing precision and durability.
Patent Information
- Application Number
- FR2025000203
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-01-12
- Filing Date
- 2025-01-09
- Publication Date
- 2025-07-18
AI Technical Summary
Existing drill bits face challenges in maximizing positioning accuracy at the start of drilling operations, particularly on smooth or obliquely oriented surfaces, and suffer from mechanical wear and brittleness leading to chipping, especially in carbide drills.
A drill bit design featuring at least three main cutting surfaces that converge at a pointed drill tip, with edge-free surfaces transitioning into flutes, eliminating transverse cutting surfaces and minimizing edges through a single continuous grinding process, ensuring high positional accuracy and reduced wear.
The design achieves precise initial positioning and minimizes wear by eliminating edges, reducing the risk of lateral displacement and material degradation, particularly suitable for carbide drills.
Smart Images
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Abstract
Description
Title of the invention: Drill bit and method of manufacturing a drill bit Background to the invention
[0001] The invention relates to a drill bit and a method of manufacturing a drill bit.
[0002] The geometry and design of a drill tip are generally critical in a drill bit. In this context, the interaction of the cutting surfaces, clearance surfaces and flutes is important.
[0003] Typical drill bits comprise two main cutting surfaces and a flute associated with each of them. The flute often extends spirally along a shank of the drill bit. Also known, in addition to solid carbide drill bits, are modular drill tools in which a reversibly exchangeable drill head can be attached to a shank.
[0004] A drill bit having two main cutting surfaces which are connected to each other in a drilling center via a transverse cutting surface can be obtained from the invention described in EP 1 230 058 B1. The clearance surfaces are each designed as a curved surface of the respective main cutting surface, which is designed to be edge-free in the direction of the flute.
[0005] A drill bit comprising three main cutting surfaces, which are connected to each other by transverse cutting surfaces and which have a complex cutting geometry overall, can be obtained from the invention described in US 2011 / 0085868 AL
[0006] In drills, the problem often arises of maximizing positioning accuracy at the start of the drilling operation. Especially in the case of smooth surfaces or surfaces oriented obliquely to a longitudinal axis of the drill, the problem often arises that the drill will be somewhat laterally offset from a desired target position. In addition, the end faces of drills are subjected to a high mechanical friction load, especially with hard materials, which can lead to significant wear. The additional problem in the case of carbide drills is that, although they have a high hardness, they also have a high brittleness, so that point loads can lead to scratching activity, which can lead to chipping of the drill material. Subject of the invention
[0007] Based on the foregoing information, the invention aims to specify a drill bit and a method of manufacturing the same, the drill bit being characterized by high positional accuracy and low wear. Realization of the object
[0008] The object according to the invention is achieved by a drill bit which extends along an axis of rotation and has at least three, preferably exactly three, main cutting surfaces. From a nose arranged on a radius, these cutting surfaces each extend in the direction of the axis of rotation. The at least three main cutting surfaces converge on a drill tip. Furthermore, starting from the drill tip and along the radial extent of the respective main cutting surface, a respective main cutting surface adjoins an edge-free surface in the circumferential direction. This edge-free surface also comprises the at least one portion of a clearance surface, which portion transforms, in each case, into a respective flute.
[0009] It should first be emphasized that a respective main cutting surface extends to the drill tip, and thus extends to the axis of rotation. The drill tip is arranged on the axis of rotation. The main cutting surfaces converge at a common point. The drill tip is therefore pointed. The pointed drill tip allows for high initial positioning accuracy because there is little or only minimal risk of lateral displacement at the start of the drilling operation. In contrast, conventional drills with transverse cutting surfaces have this problem.
[0010] In the present context - within the framework of manufacturing tolerances - "tip" surface means a surface with a diameter of less than 100 μm and in particular less than 20 μm. The drill tip is therefore formed within manufacturing tolerances by a location where the main cutting surfaces meet.
[0011] It should be particularly emphasized that the main cutting surface - starting from the drill tip and up to the nose - adjoins an edge-free surface in the circumferential direction, which edge-free surface forms at least partially, and preferably completely, the clearance surface extending to the flute. The term "clearance surface" generally refers to a surface which adjoins a respective main cutting surface, inclined to a horizontal plane (the plane perpendicular to the axis of rotation), and which extends to the respective flute. The clearance surface forms a clearance angle to such a horizontal plane and is typically of the order of several degrees.
[0012] It should also be emphasized that this clearance surface, which adjoins the respective edge-free main cutting surface, extends to the drill tip. In the case of conventional drills, the at least one cross-cutting surface and, in addition, a so-called "tip", is typically introduced in the central region and is formed by separate grinding. A step, and thus an edge, in the direction of the clearance surface is generated by means of the separate grinding step. By then providing an edge-free design for each surfaces that adjoin the respective main cutting surfaces, wear is minimized due to the absence of edges. This design is also particularly suitable for carbide drills because the absence of an edge in the highly stressed front end region of the drill avoids point or line loads, which can lead to high scratch activity and chipping of the material.
[0013] Said object is also obtained by a method for manufacturing said drill, whereby the edge-free surfaces are formed using a grinding method, and whereby only one respective grinding step is provided for each edge-free surface. The entire edge-free surface is therefore obtained only in a single continuous grinding step without multiple attachments of the grinding disc. Preferably, the complete surface, which adjoins a respective cross-sectional surface and extends in the circumferential direction up to the flute, thus also comprising the complete flank surface, is preferably ground only in a single grinding step. The grinding disc and the drill are suitably moved in a three-dimensional movement sequence, continuously and without withdrawal relative to each other.As a result of the continuous movement, the grinding disc is therefore continuously moved relative to the drill along a specified path. Since this relative movement is not stopped or interrupted, the formation of edges is reliably avoided.
[0014] The term "edge-free" therefore refers in particular to a surface progression in which no sharp edges are formed between adjoining surface sections. The term "sharp edges" also refers to transitions between adjoining surface sections with a radius of up to a maximum of 3% of the drill diameter and preferably up to a maximum of 1% of the drill diameter mm.
[0015] Advantageously, the drill bit therefore does not comprise any transverse cutting surfaces, i.e. it is designed without transverse cutting surfaces. The particular advantage thus obtained is that each radial section of the drill bit contributes to the cutting, and that, as is the case in conventional designs comprising transverse cutting surfaces, no cutting action is obtained in the region of the transverse cutting surfaces. The lack of transverse cutting surfaces in particular also contributes to the high positioning accuracy.
[0016] The term "cross-sectional surface" generally refers to a cutting region between the axis of rotation and the beginning of a tip.
[0017] In the preferred embodiment, a tip region of the drill is formed solely by edge-free surfaces that adjoin the respective main cutting surface. Therefore, in a drill comprising three cutting surfaces, the tip region is formed solely by the three cutting surfaces. main cutting surfaces, the pointed bit and the three edge-free surfaces. In this context, the tip region is defined as the foremost axial region of the drill extending from the bit to an axial length corresponding to at least 1 / 4 of the radius, in particular at least 1 / 3 of the radius, and preferably at least half of the radius. As a result, from the drill tip and at least up to the axial length defined by it, no edges are therefore present on the surfaces adjoining the main cutting surfaces.
[0018] The tip region, and thus its axial length starting from the drill tip, preferably ends at an axial length with a first full bit diameter, i.e. at an axial position of the drill where a bit is not tapered by grinding or other measures in the region of the end face at the end of the drill. The bit diameter is normally defined by the remaining circular diameter of the drill at a specified flute depth in the flute region. The bit diameter is therefore generally defined by a nominal radius of the drill minus the flute depth. In particular, this axial length therefore also defines the axial position where the clearance surface transitions into the respective flute, i.e. where the flute begins. This transition into the flute is optionally achieved by a rounding or an edge.
[0019] In the preferred embodiment, exactly three main cutting surfaces are formed, and the three edge relief surfaces are in particular formed as tetrahedral surfaces of a gradient tetrahedron which is twisted about the rotation axis. In the present context, the term "gradient tetrahedron" refers to a three-dimensional structure which is conceptually formed by the three edge-free surfaces initially forming surfaces of a tetrahedron which extends from a tetrahedron tip to a base, and the base of this tetrahedron is twisted about the rotation axis, while the tetrahedron tip is simultaneously fixed. This gradient tetrahedron thus formed forms in particular the tip region previously defined.
[0020] In the advantageous embodiment, the respective main cutting surface - seen from above - extends curved and, in particular, convexly curved in the drill tip. Therefore, preferably, no linear progression of the cross-cutting surface is formed in the region of the drill tip. Due to the convex curvature, the region close to the center of the main cutting surface, also referred to hereinafter as the central inner region, is, during drilling, arranged in front of the outer cutting surface sections which are further outward in a radial direction.
[0021] In the preferred embodiment, the respective main cutting surface in this central inner region is therefore designed to be continuously, i.e., regularly, curved. In the present context, the term "near inner region "from the center" means a region close to the center from the axis of rotation, which extends in the radial direction over more than 1 / 4 of the radius, in particular over more than 1 / 3 of the radius and for example up to half of the radius. In this case, the radius of curvature may change. The central inner region correspondingly adjoins another outer region which correspondingly extends over at least 1 / 3 of the radius, for example at least half of the radius.
[0022] Preferably, the main cutting surface is curved only in a single manner in the central inner region and furthermore over its entire length from the beak to the pointed drill tip, i.e. it does not comprise multiple counter-rotating curved (convex-concave) cutting surface sections.
[0023] Preferably, in addition to the curved cutting surface section in the central inner region, the main cutting surface further comprises a linear section in the outer region. The entire main cutting surface is preferably formed by the curved (convex) cutting surface section in the central inner region and by a linear cutting surface section in the outer region, which adjoins the curved cutting surface section and extends to the beak.
[0024] The drill bit is preferably designed as a one-piece drill bit. Furthermore, the drill bit is preferably made of carbide.
[0025] In principle, there is also the option of designing the drill as a modular drilling tool comprising a shank having an interchangeable drill tip portion inserted on the end face. This portion has the specific geometry comprising the main cutting surfaces and the edge-free surfaces adjoining them. Preferably, this drill tip portion already comprises flute portions, which then transform into flutes formed in the shank. Such a drill tip portion is attached to the shank in a suitable manner. In this context, it is often provided that the drill tip portion is rotated relative to the shank about the rotation axis for insertion. Description of the drawings
[0026] An exemplary embodiment of the invention is explained in more detail below with reference to the drawings. These drawings represent the following partially simplified illustrations:
[0027] [Fig.l] is a sectional side view of the drill bit,
[0028] [Fig.2] is a top view of a front face at the end of the drill bit,
[0029] [Fig.3] is a cross-sectional view of the drill bit at an axial length of the total diameter of the wick, and
[0030] [Fig.4] is a sectional side view of the drill bit for clarifying a tip region. Description of the implementation example
[0031] The drill bit 2, shown in [Fig.l] and [Fig.2], respectively in side view and in sectional front top view, is designed as a single-piece drill bit 2. However, the following statements apply equally to, for example, modular drill bits in which a drill tip portion is interchangeably attached to a drill shank.
[0032] The drill bit 2 generally extends along an axis of rotation 4, about which the drill bit rotates during operation. The end face at the end of the drill bit 2 comprises a plurality, specifically a total of three, main cutting surfaces 6, each extending outwardly from a pointed drill tip 5 on the axis of rotation 4 to a nose 8.
[0033] A radial distance between the axis of rotation 4 and a respective beak 8 defines a radius r.
[0034] An edge-free surface 10 adjoins each of the main cutting surfaces. 6 along a circumferential direction U, starting in particular along the entire length of the main cutting surface 6 and proceeding from the pointed drill tip 5 to the nose 8. During its further progression, this edge-free surface 10 transforms into a flute 12 in the circumferential direction U. The edge-free surfaces 10 thus also define a clearance surface 14. The transition from the edge-free surface 10 and thus from the clearance surface 14 to the wall surface of the flute 12 is indicated in FIGS. 1 and 2 by a curved line L, which is designed for example as an edge, or as a rounded transition. From the beak 8, a secondary cutting surface 14 extends along the flute 12, which cutting surface adjoins a secondary cutting surface nose 16 in the circumferential direction U.
[0035] The drill bit 2 generally comprises a tip region 20 which will be explained with reference to [Fig.3] and [Fig.4]. In this context, the longitudinally leading region of the drill 2 refers to the region extending from the drill tip 5 to a horizontal plane H, which is oriented perpendicular to the axis of rotation 4 and defines the start of the flutes 12. The tip region 20 has an axial length A, which is defined by the distance from the drill tip 5 to the horizontal plane H. From the drill tip 5, a full, i.e. maximum, bit diameter D is first reached at the horizontal plane H. The bit diameter D is generally defined as the diameter of a central region of the drill, which is called the bit 22, which comprises circular surfaces in the region of the flutes 12. The tip region 20 of this bit 22 tapers, so that the bit diameter D tapers.
[0036] The end region 20 is therefore generally the foremost region of the drill, where no flutes 12 are (yet) formed. At least in the tip region 20, all the front face surfaces are designed only as edge-free surfaces 10.
[0037] As can be seen in particular in the top view according to [Fig. 2], a respective main cutting surface 6 in the exemplary embodiment first extends linearly in an outer region 24, from the beak 8, to then extend curvedly, i.e. convexly curved, in the central inner region 26. In the exemplary embodiment, the transition between the linearly extending outer region 24 and the central inner region 26 is approximately equal to half the radius r.
[0038] The main cutting surfaces 6 therefore extend in a curved manner into the pointed drill tip 5, therefore up to the axis of rotation 4.
[0039] Considering the front geometry of the drill 2 described here, and in particular in the tip region 20, it should be emphasized that, on the one hand, the main cutting surfaces 6 extend continuously from the nose 8 to the drill tip 5 located on the axis of rotation 4 and meet at this location. No transverse cutting surface is therefore formed in the central region of the axis of rotation 4.
[0040] It should also be emphasized that the edge-free surfaces 10 directly adjoin the main cutting surfaces 6 over their entire length. In the exemplary embodiment, these edge-free surfaces 10 extend to the start of a respective flute 12.
[0041] This design allows for positionally precise fixing and drilling. The edge-free surfaces 10 also allow for minimizing wear and stress on the end faces. The drill bit 2 is in particular a solid carbide drill bit. Due to the edge-free design, the risk of local load peaks, which can lead to material degradation, is in particular also minimal.
Claims
Claims
1. Drill (2), which extends along an axis of rotation (4) and comprises at least three main cutting surfaces (6) which, from a nose (8) arranged on a radius (r), each extend in the direction of the axis of rotation (4), characterized in that, from a drill tip (5) and over the entire radial extent thereof, the at least three main cutting surfaces (6) converge on the drill tip (5), and each cutting surface (6) adjoins a respective edge-free surface (10), which comprises a clearance surface (14) and in each case transforms into a respective flute (12).
2. Drill (2) according to the preceding claim, characterized in that the main cutting surfaces (6) converge on the drill tip (5) without the presence of transverse cutting surfaces.
3. Drill (2) according to any one of the preceding claims, characterized in that a tip region (20) of the drill (2) is formed solely by the edge-free surfaces (10), wherein the tip region (20) extends from the drill tip (5) to an axial length (A) which corresponds to at least 1 / 4 of the radius (r), in particular at least 1 / 3 of the radius (r), and preferably at least 1 / 2 of the radius (r).
4. Drill bit (2) according to any one of the preceding claims, characterized in that exactly three main cutting surfaces (6) are formed, and the three edge-free surfaces (10) are designed in the manner of tetrahedral surfaces of a gradient tetrahedron which is designed to be able to rotate on itself around the axis of rotation (4).
5. Drill bit (2) according to any one of the preceding claims, characterized in that a respective main cutting surface (6) extends curvedly into the drill bit tip (5).
6. Drill (2) according to the preceding claim, characterized in that a central inner region (26) of the respective main cutting surface (6) extends continuously in a curved manner into the drill tip (5), wherein the central inner region is greater than 1 / 4 of the radius (r), in particular greater than 1 / 3.
7. Drill bit (2) according to either of the two preceding claims, characterized in that the respective main cutting surface (6) is curved in only one direction.
8. Drill bit (2) according to any one of the preceding claims, characterized in that it is designed as a one-piece drill bit (2), in particular made of carbide.
9. A method of manufacturing a drill bit (2) according to any preceding claim, wherein the edge-free surfaces (10) are introduced in a single grinding step using a grinding process.